Engine noise depressing assemblies

ABSTRACT

Noise depressing devices are provided for use in conjunction with engines of the type commonly used to power model aircraft, boats, cars and the like. The noise depressing devices include: (1) an elongated extension sleeve that is secured to and aligns at one of its ends with the exhaust port of an engine and (2) a plurality of spaced baffle plates secured to the opposite end of the sleeve that are designed to quietly diffuse the exhaust gases into the atmosphere.

United States Patent [191 Broberg, Jr.

[ 1 ENGINE NOISE DEPRESSING ASSEMBLIES [76] Inventor: Dewey O. Broberg, Jr., Rt. 1, Box

102, Long Grove, 111. 60047 [22] Filed: 0C1. 26, 1972 [21] Appl. No.: 301,178

[52] US. Cl 181/56, 181/36 R, 181/46, 181/49, 181/60, 181/69 [51] Int. Cl. F01 H08 [58] Field Of Search 181/34, 35 R, 36 R, 181/40, 41, 46, 47, 49, 56, 57, 59, 60, 69, 72

[56] References Cited 1 UNITED STATES PATENTS 2,954,839 10/1960 Gibel 181/56 3,669,216 6/1972 Spies 1. 3,497,031 2/1970 Kedziora 181/40 Dec. 18, 1973 Haining 181/59 Murphy 181/40 [57] ABSTRACT Noise depressing devices are provided for use in conjunction with engines of the type commonly used to power model aircraft, boats, cars and the like. The noise depressing devices include: (1) an elongated extension sleeve that is secured to and aligns at one of its ends with the exhaust port of an engine and (2) a plurality of spaced baffle plates secured to the opposite end of the sleeve that are designed to quietly diffuse the exhaust gases into the atmosphere.

8 Claims, 7 Drawing F igures PATENIEDDEC18|975 3379,1342 sum 10F 3 Q Ill? 52 PATENTEDUEC 1 8 ms 3; 779342 sum 2 OF 3 smear 3 of 3 PATENIEDBH; 18 4925 NM a j k Q N% AN 1:11-151 Q g MUN K N MN ml ENGINE NOISE DEPRESSING ASSEMBLIES BACKGROUND OF THE INVENTION The present invention relates generally to noise depressing devices and more specifically to light-weight, simplified mufflers useful in reducing exhaust engine noises emitted from engines of the type commonly used to power miniature aircraft, cars, boats and models.

In recent times, the use of high rpm. engines to power model aircraft and the like has become quite widespread, primarily as a consequence of the increased leisure time available to many persons interested in engaging in model airplane type hobbies. Certainly, almost anyone who has participated in such hobbies, or who has watched others participate, is aware of the highly objectionable, high-pitched whine or noise that is emitted from the type engines used to power the model airplanes, boats, cars or the like. In many instances, for example, these undesirable noise levels have become so objectionable that they interfere with the enjoyment of the hobby. In fact, some communities have even enacted restrictive ordinances to control the noise levels of model engines.

As a consequence of the increased demand for such engines and the equally increased desire for significant reductions in noise levels, an urgent need has developed for a low-cost, but effective, muffler device that can reduce noise levels generated by such engines without unnecessarily reducing their power output.

Conventional muffler devices are either too large and difficult to fabricate, or are too expensive and result in excessive power losses in the engines themselves. Even more importantly, however, no currently available muffler system effectively reduces engine exhaust noise to an acceptable level or is easily adaptable to various size engines.

It is the primary object of this invention, therefore, to provide a simplified, light-weight muffler or exhaust noise depressing device that can be easily attached to existing types of engines and yet, when assembled, will allow engine exhaust gases to quietly diffuse into the atmosphere. 1

Secondarily, of course, it is a further object of this invention to provide an exhaust noise depressing device that can reduce noise levels without causing engine exhaust back-pressure and significant reductions in engine power.

Moreover, it is an object of this invention to provide a muffler system that can be easily adapted to existing engine exhaust ports,- can be easily installed and still is low-cost, easily fabricated, long-lasting and efficient.

SUMMARY OF INVENTION According to this invention, exhaust engine noises are depressed by means of a muffler assembly in which an elongated, hollow extension sleeve is secured to the exhaust portion of the engine and a plurality of spaced baffle plates are secured to the opposite end of the elongated extension sleeve. Exhaust gases discharging from the engine exhaust port, therefore, pass through the elongated extension sleeve and then diffuse in a quiet fashion through the spaces formed between the spaced, parallel aligned baffle plates.

BRIEF DESCRIPTION OF THE DRAWINGS The structural details of various illustrative embodiments of this invention, as well as the numerous advantages of the invention, will be more readily understood by reference to the accompanying drawings in which:

FIG. I is a side elevational view of an engine and muffler assembly embodiment of this invention with the muffler assembly shown in cross-section.

FIG. 2 is a top plan view of an engine and muffler assembly illustrated in FIG. 1 with both the engine and muffler being shown in cross-section.

FIG. 3 is an elevational view of the upper portion of an engine and mufiler assembly showing a modified system for mounting the muffler onto the engine.

FIG. 4 is a cross-sectional view of the engine and muffler illustrated in FIG. 3 taken across line 4-4.

FIG. 5 is a fragmentary perspective view of the various bafile plates and spacers used at the outermost end of the muffler assembly.

FIG. 6 is a perspective view of an alignment adaptor plate or position key used in the engine and muffler embodiments illustrated in FIGS. 1 and 2 which is used to easily adapt the mufiler assembly to differently sized exhaust port openings for differently sized engines.

FIG. 7 is a diagramatic top plane view of the muffler assembly illustrated in FIGS. 1 and 2 with the various parts of the muffler in an unassembled state.

DETAILED DESCRIPTION OF THE EMBODIMENTS Referring specifically to the drawings, and particularly FIGS. 1 and 2, one embodiment of a noise depressing device or muffler 10 of this invention is shown in an attached relationship with a conventional model airplane engine 12. It should be understood, of course, that although the muffler devices of this invention can be used with various types of engines, for purposes of illustration, only a standard two-cycle model airplane engine is shown in the drawings. Typically, the type engines 12 used in conjunction with the muffler devices 10 of this invention are internal combustion engines having a crank-case 14, an upwardly projecting cylinder l6, and an elongated slot-like exhaust port 18 which projects laterally from one side of cylinder 16 and provides a discharge point for exhaust gases emitted from the engine. Various other parts of a typical engine, such as a carburetor, fuel line, throttle, or fuel adjustment rod and propeller, are not shown in the drawings since they are not needed to fully describe the parts and operation of the muffler systems of this invention.

The mufflers or noise depressing devices of this invention generally include an elongated exhaust port extension sleeve 21, which is secured at one end to engine exhaust port 18 by means of clamp band 23, and which also includes, at its opposite end, a plurality of spaced baffle plates 25, which are secured to sleeve 21 by means of assembly screws 27. As shown specifically in FIGS. 1 and 2, exhaust port extension sleeve 21 is hollow, is constructed from a tubular material and is adapted to mesh at one end with the exhaust port 18 of the engine. As mentioned previously, sleeve 21 is firmly secured to engine 12 by means of clamp band 23 which extends around the periphery of upwardly projecting cylinder 16. Opposite ends of the clamp band 23 are secured to the lateral edges of sleeve 21 by assembly screws 29. Worm screw 30, in turn, acts as a tightening device for clamp band 23, and is first turned in one direction to loosen clamp band 23 and permit it to be easily slipped over the top of cylinder 16 and then is turned in an opposite direction to tighten the muffler assembly and clamp band 23 in a firmly secure position when the extension sleeve 21 is in a meshed relationship with engine exhaust port 18.

The spaced baffle plates 25, disposed at the outermost end of sleeve 21, are maintained in a spaced relationship by means of spacing washers 32 which are placed between each adjacent plate 25. By means of baffle plates 25 and spacing washers 32, a plurality of small openings 34 are provided in muffler 10. These openings 34, of course, permit exhaust gases discharging through sleeve 21 to diffuse in a controlled manner into the atmosphere when engine 12 is in operation and, thus, provide a muffling effect that drastically reduces the operational noise levels for the engine.

As shown in FIGS. I4, and specifically in FIG. 5, a series of nine spaced baffle plates 25 are arranged in an adjacent relationship, each plate being separated a predetermined distance from the next adjacent plate by means of spacing washers 32. Each baffle plate is not only provided with a plurality of slots 40, which permit diffusion of the exhaust gases emitted from the engine 12, but each plate is also provided with a pair of oppositely disposed openings 41 through which assembly screws 27 pass. End plate 42, which is placed at the outermost end of the spaced baffle plates 25, has no slots, but instead is designed to block the flow of exhaust gases and direct such flow only through slots 40 in plates 25 and, in turn, through openings 34 formed between the spaced baffle plates 25.

It should be understood, of course, that the muffler devices of this invention can be easily assembled, first by securing sleeve 21 in place by means of clamp band 23, next by aligning baffle plates 25 in a spaced adjacent relationship, with pairs of spacing washers 32 being used to maintain appropriate spacing between adjacent plates, and finally by passing assembly screws 27 through the openings 43 in end plate 42, through the first pair of washers 32, through the openings 41 in baffle plates 25, through another pair of washers 32 and so forth until the entire structure of baffle plates 25 and spacing washers 32 is assembled. It should be noted that the opposite edges of sleeve 21 are provided with a pair of threaded holes 44 into which assembly screws 27 are tightened to secure the entire baffle plate assembly.

Naturally, it is desirable that the muffler systems 10 of this invention be universally adaptable to fit nearly any conventional engine currently available. Since various available engines have differently sized exhaust ports 18, it is preferable in the practice of this invention to utilize a pair of alignment adaptor or position keys 50 which fit between engine exhaust port 18 and exhaust port extension sleeve 21. As a result of the tight fit and support provided by the keys 50 a tight sealing engagement of exhaust port 18 and sleeve 21 is achieved by the securing means. One such adaptor key 50 useful in the practice of this invention is shown generally in FIG. 6. The cross-shaped key 50 shown in FIG. 6 includes edges 51 and 52, which are designed to fit tightly within the confines of upper and lower walls 60 and 61 of sleeve 21 (FIG. 1), and opposite edges 53 and 54, which are designed to fit tightly within the upper and lower walls 63 and 64 of engine exhaust port 18. If, for example, a relatively narrow opening is provided by walls 63 and 64 of engine exhaust port 18, then edges 53 and 54 of key 50 can be filed down to an appropriate size to insure a tight seal and fit between the elongated sleeve 21 of muffler 10 and the exhaust port 18 of engine 12.

In cases where the opening size of elongated sleeve 21 is substantially identical to that of exhaust port 18, adaptor key 50 is not required. In such instances, for

' example, as shown in FIGS. 34, muffler assembly 10 can be secured to the engine by means of assembly screws 70, which fit through bores 71 in exhaust port 18 and are threadably engaged at 72 to elongated sleeve 21.

FIG. 7 illustrates diagramatically the entire muffler assembly-embodiment of FIGS. 1 and 2 in an unassembled state. Specifically, the series of baffle plates 25 are shown in an aligned, side-by-side relationship prior to assembly with spacing washers 32 interposed between each baffle plate. As mentioned previously, two assembly screws 27 are provided to fit through the aligned baffle plates 25 and spacing washers 32 to secure the baffle assembly to sleeve 21. In addition, lock washers are provided between assembly screws 27 and end plate 42 to insure that baffle plates 25 will not loosen during operation of the muffler assembly.

Again, as mentioned previously, alignment adaptor keys 50 are provided to adapt the opening in exhaust port 18 with the opening in sleeve 21 to insure a gastight fit between sleeve 21 and exhaust port 18. It should also be noted, however, that an adaptor blank 81 having a varying size opening 82 can also be used in the practice of this invention to insure a gas-tight fit between sleeve 21 and exhaust port 18.

It has been found that adaptor blank 81 is particularly useful in the practice of this invention when opening in exhaust port 18 is substantially smaller than the opening in sleeve 21. Specifically, opening 82 in blank 81 is sized exactly to correspond to the opening in exhaust port 18. Then, when the blank 81 is placed between exhaust port 18 and sleeve 21, blank area 83 closes off any excess open areas in sleeve 21 and insures a gas-tight seal between sleeve 21 and exhaust port 18.

Although a wide variety of materials can be used in constructing the mufiler assembly of this invention, it has been determined that elongated sleeve 21 is desirably constructed from aluminum, while baffle plates 25 and end plate 42 are desirably constructed from steel. It has been found, for example, that the hot exhaust gases emitted from the engine tend to expand sleeve 21. If an identical material, such as aluminum, it used for baffle plates 25, however, the plates also expand and tend to bend or deform in such a manner as to increase the size of the exhaust gas diffusion openings 34 and reduce the noise depressing ability of the muffler. Accordingly, it is desirable in the practice of this invention that the baffle plates 25 and end plates 42 be constructed from a material that is far less expandable when heated than the material used for sleeve 21.

It has also been found that the most efficient noise depression can be accomplished when the openings 34 between adjacent baffle plates 25 are maintained in the range of about .005 to .010 inch. In other words, the most desirable distance between adjacent baffle plates 25 to accomplish effective gas diffusion without the loud cracking engine sound is about .005 to .010 inch. Of course, this spacing can be varied, depending upon the type materials used for baffle plates 25, the relative size of slots 40 and' thequantity-of exhaust gases generated by the particular engine. It is contemplated in the practice of this invention, therefore, that the size of slots 40 and the spacing between baffle plates 25 be adjusted to permit the maximum amount of, exhaust gas diffusion without significant impairment of the noise reducing ability of the muffler. Similarly, it should be understood that more or less than nine baffle plates 25 can be used for any given engine to increase or decrease the ability of the muffler assembly to quietly diffuse exhaust gases into the atmosphere.

The numerous advantages of the muffler assemblies of this invention are apparent from the foregoing description. The muffls have a simplified construction,

are light-weight and can be easily assembled or disasvwide-scale use. Moreover, it has been recognized through this invention that exhaust gases can be quietly diffused into the atmosphere through a plurality of spaced baffle plates in a stage-wise fashion, without a significant build-up of back pressure for the engine and the consequent reduction in engine power output.

Naturally, it should be understood that the foregoing embodiments are merely illustrative of the muffler invention and the entire concepts of stage-wise noise depression and exhaust gas diffusion. Accordingly, it is intended that the foregoing embodiments can be altered or modified without departing from the spirit and scope of the invention as claimed.

I claim:

1. A universally adaptable noise depressing device for a combustion engine, adaptable for use with differently sized engines having varying engine displacement and exhaust port characteristics comprising:

a tubular sleeve means secured to said engine and aligned at one end with the exhaust port thereof for defining an extended chamber for receiving exhaust gases emitted from said engine;

a plurality of spaced baffle plates removably secured to the opposite end of said tubular sleeve means which define a plurality of openings through which exhaust gases emitted from said engine are diffused in a stage-wise fashion into the atmosphere, said baffle plates having a plurality of registered openings formed therein to successively transmit said exhaust gases and said plates being successively arranged in a series transversely to said tubular sleeve means;

means for removably securing said baffle plates to said tubular sleeve so that varying numbers of said plates can be arranged in said series; spacing means disposed between adjacent baffle plates to maintain said plates in a spaced relationship with respect to each other and to separate each of said plates a predetermined distance from each succeeding plate; and i an alignment adaptor means disposed between and extending within said tubular sleeve means and said engine exhaust port to maintain said port and said sleeve means in an aligned, sealed relationship.

2. The noise depressing device of claim 1 wherein said baffle plates are maintained in a spaced position relative to one another and wherein the distance between each adjacent plate is in the range of about .005 to .010 inch.

3. The noise depressing device of claim 2 wherein said spacing means are spacing washers.

4. The noise depressing device of claim 1 wherein said tubular sleeve means is constructed from a material that is relatively more heat expandable than the material from which said baffle plates are constructed.

5. The noise depressing device of claim 1 which is further characterized by including means for securing said tubular sleeve means to said engine.

6. The noise depressing device of claim 5 wherein said means for securing said tubular sleeve means to said engine is a clamp band which surrounds said engine and is secured at its opposite ends to said tubular sleeve means.

7. The noise depressing device of claim 1 wherein said alignment adaptor means is a cross-shaped key having four oppositely disposed edges, one of said edges fitting within said exhaust port and an opposite of said edges fitting within said tubular sleeve means.

8. The noise depressing device of claim 7 wherein the edge of said cross-shaped key fitting within said exhaust port is adjustable to differently sized exhaust port openings. 

1. A universally adaptable noise depressing device for a combustion engine, adaptable for use with differently sized engines having varying engine displacement and exhaust port characteristics comprising: a tubular sleeve means secured to said engine and aligned at one end with the exhaust port thereof for defining an extended chamber for receiving exhaust gases emitted from said engine; a plurality of spaced baffle plates removably secured to the opposite end of said tubular sleeve means which define a plurality of openings through which exhaust gases emitted from said engine are diffused in a stage-wise fashion into the atmosphere, said baffle plates having a plurality of registered openings formed therein to successively transmit said exhaust gases and said plates being successively arranged in a series transversely to said tubular sleeve means; means for removably securing said baffle plates to said tubular sleeve so that varying numbers of said plates can be arranged in said series; spacing means disposed between adjacent baffle plates to maintain said plates in a spaced relationship with respect to each other and to separate each of said plates a predetermined distance from each succeeding plate; and an alignment adaptor means disposed between and extending within said tubular sleeve means and said engine exhaust port to maintain said port and said sleeve means in an aligned, sealed relationship.
 2. The noise depressing device of claim 1 wherein said baffle plates are maintained in a spaced position relative to one another and wherein the distance between each adjacent plate is in the range of about .005 to .010 inch.
 3. The noise depressing device of claim 2 wherein said spacing means are spacing washers.
 4. The noise depressing device of claim 1 wherein said tubular sleeve means is constructed from a material that is relatively more heat expandable than the material from which said baffle plates are constructed.
 5. The noise depressing device of claim 1 which is further characterized by including means for securing said tubular sleeve means to said engine.
 6. The noise depressing device of claim 5 wherein said means for securing said tubular sleeve means to said engine is a clamp band which surrounds said engine and is secured at its opposite ends to said tubular sleeve means.
 7. The noise depressing device of claim 1 wherein said alignment adaptor means is a cross-shaped key having four oppositely disposed edges, one of said edges fitting within said exhaust port and an opposite of said edges fitting within said tubular sleeve means.
 8. The noise depressing device of claim 7 wherein the edge of said cross-shaped key fitting within said exhaust port is adjustable to differently sized exhaust port openings. 